This invention relates generally to a socket for mounting an electronic device such as a semiconductor device, or the like, and more particularly to a socket which is to be used in burn-in tests for such devices.
Defects in a semiconductor device are initially checked by subjecting the semiconductor device (which may be referred to as an IC device or an IC package) to a burn-in test. In connection with a burn-in test, the semiconductor device is mounted on or in a socket. According to sockets of the pop-up type which are widely used, a cover member of the socket engages in alternating motion in a direction toward and away from the main base thereof. This type of straight-line movement of the cover member is suitable for automatic loading of a semiconductor device.
The surface-loading type semiconductor devices in which a plurality of terminals are arranged in an X-Y matrix as in the case of BGA (ball grid array) or CSP (Chip Sized Package) are increasing in number, and sockets which can be used for these are being developed. In the case where a BGA package or a CSP package is mounted on a circuit substrate, there may be problems of defective soldering stemming from irregularities in the height of the balls or the deformation of one or more balls. It is desirable that the lower surface (the loading side) of the ball be free of damage. In the case where the ball is made of a low melting point substance such as solder, etc., there are cases where it tends to be softened in the high temperature state at the time of a burn-in test, with the solder balls becoming deformed.
In order to avoid such a problem, as shown in U.S. Pat. No. 6,083,013, issued Jul. 4, 2000, one approach provides a contact terminal which regulates the amount of contact protrusion from a floating member which seats an IC device at the end of the contacts, thereby leveling the protrusion heights of the solder balls.
Nevertheless, there is the following problem in this approach: With reference to FIG. 12, a floating member 2, capable of vertical movement relative to the main socket body 1, is provided with a stop mechanism for regulating the amount of protrusion of the contact end. Because of this, contact terminals 6 protrude from floating member 2 at all times including the time of loading of IC package 4, with solder balls 3 of the IC package 4 being in contact with the contact terminals 6. As a result, solder balls 3 can be caught by the contact terminals 6 thereby interfering with loading of the IC package. Further, it is impossible for the IC package to be loaded in the socket without a possibility that at least some solder balls 3 are scraped during the loading procedure.
An object of the present invention is the provision of a socket which overcomes the above noted prior art limitation and which properly loads semiconductor devices of the surface loading type such as BGA or CSP.
Another object of the invention is the provision of a socket which is capable of controlling any deformation of a protrusion-like or a bump-shaped terminal of a semiconductor device to be loaded. Still another object is the provision of a socket in which the amount of deformation of the terminals of semiconductor devices of the surface loading type can be adjusted.
Yet another object of the invention is the provision of a socket having a latch mechanism having improved operability, is economical and which is suitable for automatic loading of semiconductor devices.
According to the invention, contact regulating means for the regulation of the position of the movable ends of a plurality of contacts is provided in a socket comprising a base member, a cover which is mounted for alternating motion toward and away from the base member, a plurality of contacts that have been fixed to the base member body and an adaptor for seating the electronic device. The contact regulating means is provided on the base member and the adaptor is movably mounted on the contact regulating means. A plurality of through-holes are formed in the adaptor in conformity with the plurality of contacts and, when the adaptor has been moved toward the contact regulating means, the movable ends of the contacts protrude from the through-holes of the adaptor. Since the movable ends of the contacts are regulated to a certain fixed protrusion height by the contact regulating means, the protrusion height of the movable ends of the contacts that protrude from the adaptor is also regulated. When the adaptor touches the contact regulating means, the amount of protrusion of the movable ends of the contacts from the seating surface of the adaptor is maximized. When the adaptor is disposed at a position which is removed from the contact regulating means, the plurality of free ends of the contacts are positioned inside the through-holes without protruding from the seating surface of the adaptor.
Preferably, the contact regulating means has a plurality of slots at locations corresponding to the plurality of contacts, with a stop surface being formed in each slot to engage with or near the movable end of the contacts, thereby making it possible to regulate the protrusion height of the movable ends of the contacts.
Preferably, the adaptor can be removed from the socket and replaced with another adaptor so that the amount of protrusion of the free movable end of the contacts can be varied. In addition, the seating surface of the adaptor may include an offset surface for supporting the electronic device, and a surface which includes the plurality of through-holes at a location which is lower than the offset surface. The electronic device is a semiconductor device having a plurality of terminals arranged on one side in an X-Y matrix, such as BGA or CSP types.
Moreover, the socket made according to this invention may include a latch member that moves in linkage with the cover member. The latch member is linked to the cover member through a linkage mechanism and, when the cover member is separated from the base member, the electronic device (semiconductor device) is pressed down, thereby causing the adaptor to be pushed down. When the adaptor has been pushed down more than a certain amount, the movable end of the contacts protrude from the through-holes of the adaptor (seating surface of the adaptor), effecting contact with the terminals.
According to a feature of the invention, the latch member is rotated using first and second fulcrums changing the radius of rotation or straight-line distance between the center of the rotation and the pressing part of the latch member. The arrangement provides a rapid movement of the latch member to its retracted location using one fulcrum when the cover member has been pushed down and when the cover is allowed to ascend, back to a position where the latch engages a semiconductor device loaded in the socket. From this location, using the other fulcrum, more gradual movement is effected as the cover member is pushed up, thereby gradually increasing the pressing force that is given to the semiconductor device. As a result of this, it becomes possible to prevent any damage or deformation, particularly to thin semiconductor devices.